Adaptive response of metal-oxide memristive nanostructures to periodic electric stimulation

1.

Adaptive response of metal-oxide memristive
nanostructures to periodic electric stimulation
[email protected]
D.S. Korolev, A.I. Belov, I.N. Antonov, E.V. Okulich, A.N. Mikhaylov, O.N. Gorshkov,
S.A. Gerasimova, V.B. Kazantsev
Abstract
The adaptive response of metal-oxide memristive nanostructures based on SiO2 and ZrO2(Y) oxide dielectrics to the action of periodic electric
signal has been studied. The observed decrease in resistance of memristive device is used to imitate the active synaptic connection in a model
of two synaptically coupled neuron-like generators due to the increase in coupling strength. The proposed coupling channel provides the forced
synchronization with the parameters depending on the sensitivity range of memristive device.
Experimental details
Ion-beam simulation
Fabrication of memristive devices
Effect of ion irradiation on resistive switching parameters
Deposition:
Thin-film memristive structures were
fabricated on CMOS-compatible TiN (25
nm) / Ti (25 nm) / SiO2 (970 nm) / Si
substrate. Oxide dielectrics SiO2 and
ZrO2(Y) with thickness of 40 nm were
deposited by RF-magnetron sputtering
using
a
MagSputt
3G-2
(Torr
International) system. The top Au
electrodes (40 nm) were deposited by DC
sputtering using the same sputtering
system.
Schematic of the composition and geometry of the studied capacitor-like
structure deposited by the methods of magnetron sputtering.
Resistive switching properties
Dependence of the current values (measured at +0.5 V) in the LRS and HRS in non-irradiated (w/o irr.) devices and in
devices irradiated with 150 keV H+ ions (a), (O++Si+) ions and 15 MeV H+ ions (c) on the number of switching events after
each successive accumulation of the irradiation fluence. The irradiation was performed for the structures switched to HRS
(Irr. in HRS) and LRS (Irr. in LRS). The arrows indicate the current values changed after irradiation.
No significant change in the resistive switching parameters is observed under ion irradiation up to the
fluences corresponding to the extreme fluence of 1017 cm-2 of space protons or fission neutrons.
The lateral filament nucleus size r0 is the distance
from the axis of ion incidence at which the vacancy
concentration is reduced to 100 times with respect to
the maximum.
Typical I-V hysteresis due to bipolar resistive switching after electroforming of the SiO2- and ZrO2(Y)-based device.
The fabricated memristive devices demonstrate bipolar resistive switching behavior typical of the valencechange materials, and the resistive state is determined by the interplay between the reduction-oxidation
(redox) processes in a system of conducting pathways (filaments) grown in oxide film. Due to the stochastic
nature of filament rupture / recovery and the intrinsic asymmetry of the given phenomena, the considered
memristive device can be considered as a multi-stable nonlinear system.
Adaptive behavior of memristive devices
Ionizing radiation and Displacement damage
There are no significant
changes of forming voltage
and current-voltage
characteristics in structures
irradiated with 5 keV Xe+ ions
with the doses 1011–1014 cm-2.
The calculated depth profiles of total ionization losses in SiO2-based memristive devices irradiated with 150 keV and 15 MeV
protons with equivalent fluences (a) and displacement damage in same structure irradiated with 150 keV Si+ + O+ ions
reproducing the effect of 1 MeV neutrons (b). A.I. Belov et al. Nucl. Instr. Meth. B (2016) – DOI: 10.1016/j.nimb.2016.02.054
The effect of proton irradiation mainly originates from ionization. The ionization losses were calculated by
using the SRIM software [J.F. Ziegler et al. NIMB 268, 1818 (2010)] for protons with energies of 150 keV and
15 MeV. The comparison of calculated ionization profiles allows drawing the conclusion that the irradiation
with medium-energy protons provides one order of magnitude higher energy losses in the switching oxide
layer than in the case of irradiation with the same dose of 15 MeV protons typical of cosmic rays.
Current-voltage characteristics of non-irradiated (a) and Xe+ irradiated (b)
SiO2-based memristive structures.
Conclusions
The experiments on ion-beam simulation have demonstrated the high tolerance of SiO2-based
memristive nanostructures to the impact of high-energy protons and fission neutrons. This
opens up the possibility of the application of this type of nanostructures in the development of
memory devices suitable for operation in the conditions of high radiation exposure.
Low-energy
heavy ion irradiation of memristive nanostructures do not lead to improving the
RRAM performance and reducing the significance of uncontrollable stochastic factors. There are
some spread of RS parameters in investigated structures.
Acknowledgements
Equivalent fluences of 150 keV ions providing the same ionization losses and the same concentrations of displacements in
SiO2 layer as in the cases of 15 MeV proton irradiation with the fluence of 1013-1017 cm-2 and 1 MeV neutrons with the
fluence of 1015-1017 cm-2, respectively.
The study is supported by the Ministry of Education and Science of the Russian
Federation (RFMEFI57514X0029) and by the grant of the President of Russian
Federation (МК-3714.2015.2).
The authors are grateful to Dr., Prof. V. Kozlovskii (Peter the Great Saint-Petersburg
Polytechnic University) for conducting of proton irradiation on cyclotron.